stroboscopic (aka equivalent time sampling) using EZCAP DVB dongle ?

Leif Asbrink leif at sm5bsz.com
Sun Jul 8 19:29:10 UTC 2012


On Sun, 8 Jul 2012 12:30:05 -0500
"Jay Salsburg" <jsalsburg at bellsouth.net> wrote:

> The E4000 Tuner offers a stepping stone into the world of SDRs. 
> It does the heavy lifting, significantly reducing the size, 
> cost, and complexity of a SDR. It does not do any programmable 
> signal processing, which is where SDRs are strongest. 
> Quantization has been left out of the discussion because the 
> RTL2832 is so bad at it (to conserve size and cost). The RTL2832 
> hamstrings the usefulness of the E4000 significantly narrowing 
> the application of DSP. If you want high fidelity reception, 
> you must apply a high fidelity ADC. 

I do not understand how you think to arrive at this conclusion. 
The RTL2832/E4000 dongels allow superior quality demodulation of 
FM signals.

The suppression of neighbouring channels is limited due to
aliasing, but it is not bad and interference can be avoided
by changing the LO frequency. There is also a mirror image
but if you use Linrad you can apply the calibration procedure
that eliminates image spurs.

Now that AGC is eliminated these dongles allow a pretty good
general purpose SDR at small cost.
http://www.sm5bsz.com/linuxdsp/hware/rtlsdr/rtlsdr.htm

The high fidelity reception is in no way limited by the ADC
in these dongles as long as the desired signal is not much
weaker than surrounding signals. (Much means 50 dB or so.)

Regards

Leif / SM5BSZ




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